A call for help from gallery owner Mr. Prentice leads the three detectives into a new adventure: his apartment is said to be haunted. When the Carpathian dog, a valuable work of art, is also stolen, events spiral out of control because all the residents have a motive. As the suspects are eliminated one by one, the three detectives find themselves in the middle of their most exciting case yet.

The three investigators want to go on a road trip during their vacation, but just as they are about to set off, the phone rings and an unknown caller hands the trio of detectives their latest case: the archaeologists belonging to the secret society Sphinx are carrying out illegal excavations and selling the stolen art treasures. Their next target is the supposedly cursed island of Makatao.

During the summer vacations, the three friends are about to take a trip together to Romania, where they are allowed to complete an internship on the film set of "Dracula Rises", arranged for them by Peter's father, who is responsible for the special effects during the filming. No sooner do they arrive in Transylvania than mysterious events begin to pile up at Countess Codrina's old castle, which serves as the original setting for the film. The three detectives want to find out what all this may have to do with a boy who has been missing for over 50 years, a mysterious brotherhood and an enigmatic undead. Soon, not only the filming and Peter's relationship with his father are at stake, but also the friendship of the three investigators.

During an internship on a film set in Romania, the three detectives investigate eerie occurrences at an old castle. They uncover a mystery surrounding a missing child and a mysterious amulet. The Carpathian Hound: In Rocky Beach, an art collector's house is supposedly haunted. When a valuable crystal figurine is stolen, the boys must find the thief among the eccentric residents. Isle of the Dead: A mysterious phone call leads the trio to the volcanic island of Makatao. There, they clash with the secret society Sphinx, which will stop at nothing to get its hands on an ancient treasure.